Physiological acid base balance

The physiological acid-base balance refers to the maintenance of a stable pH in the body’s fluids and tissues, crucial for cellular functions and enzymatic reactions. The normal pH range for arterial blood is 7.35-7.45.

Regulation Mechanisms

Buffer Systems:

• First line of defense against pH changes.
• Consist of a weak acid and its conjugate base or a weak base and its conjugate acid.
• Key buffer systems include:
  • Bicarbonate Buffer System (HCO3-/H2CO3)
  • Phosphate Buffer System (HPO42-/H2PO4-)
  • Protein Buffer System (e.g., hemoglobin)

Respiratory System:

• Regulates acid-base balance by controlling CO2 levels in the blood.
• CO2 reacts with water to form carbonic acid (H2CO3), which dissociates into H+ and HCO3-.
• Acidosis: Increased breathing expels CO2, reducing H+ concentration and raising pH.
• Alkalosis: Decreased breathing retains CO2, increasing H+ concentration and lowering pH.

Renal System:

• Manages acid-base balance by excreting H+ ions and reabsorbing bicarbonate ions (HCO3-).
• Acidosis: Increased H+ excretion and HCO3- reabsorption, raising blood pH.
• Alkalosis: Decreased H+ excretion and HCO3- reabsorption, lowering blood pH.

Disorders of Acid-Base Balance

Acidosis:

• Excess acid or loss of base.
  • Respiratory Acidosis: Due to CO2 retention.
  • Metabolic Acidosis: Due to excess non-respiratory acids or bicarbonate loss.

Alkalosis:

• Excess base or loss of acid.
  • Respiratory Alkalosis: Due to excessive CO2 excretion.
  • Metabolic Alkalosis: Due to excessive H+ loss or bicarbonate accumulation.

Compensation Mechanisms

• The body compensates for imbalances through:
  • Respiratory Compensation: For metabolic acidosis, increased ventilation lowers CO2.
  • Renal Compensation: For respiratory acidosis, increased bicarbonate reabsorption and H+ excretion.
• These mechanisms work together to maintain the acid-base balance, ensuring the proper function of the body’s systems. Disturbances can lead to acidosis or alkalosis, which require prompt correction to prevent complications

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